(IDEX Online) - Diamond manufacturers in Surat are now importing the vast majority of rough direct to the city, rather than via Mumbai.In the financial year to March 2020, rough imports to both cities were on a par, at just over $6bn.But in the 10 months to February 2022, Surat imported $13.2bn of rough, almost four times as much as Mumbai's $3.7m, according to new figures from the Gem and Jewellery Export Promotion Council (GJEPC).The council says may smaller manufacturers have switched to direct importation because of improved customs facilities and fewer GST (Goods and Service Tax) formalities.Surat's long-delayed $355m bourse is due to open later this years and is expected to tempt many traders to relocate from the Bharat bourse, 175 miles away in Mumbai.The Surat Diamond Bourse (pictured), which will be the world's largest office building, with nine 15-story towers.